Homework 9

Correlation and Regression (2 points)

1. Can a correlation between the following variables from our data set be calculated (think

carefully!), and, if so, would you expect the correlation to be positive, negative, or zero?

a. The number of hours students think they should watch TV per week, and the

number of hours they do watch TV per week

b. Number of friends and transfer student status (yes vs no)

c. The number of shoes students have, and the of jobs they have had

d. The number of hours students spend at parties per week and their GPA

e. The number of shoes male students have and the number of shoes female students have.

2. How would you describe the following correlations (keep in mind size and direction)?

a. r = .35

b. r = -.60

c. r = .14

A small random sample (n=10) was drawn from the population of a statistics class at CSUN. You are interested in estimating the relationship between hours studying per week and GPA. Here is the data, in a paired list:

Studying (X) GPA (Y)

7 3.90

6 3.10

30 3.80

8 3.20

10 3.90

10 3.60

9 4.00

1 2.90

12 2.40

10 3.78

3. Calculate r for these data.

4. Write the regression equation.

5. What would the predicted GPA be of a student who studied for 5 hours per week? What

would the predicted GPA be of a student who studied for 90 hours per week?

6. Are there any issues/problems with making either of these predictions?

7. What percent of variance in GPA is explained by hours of studying?

8. Interpret the correlation (r) and the two regression coefficients (a & b).